Observation of the Ã−X̃ Electronic Transition of the β-Hydroxyethylperoxy Radical

Abstract

TheÃ-X electronic absorption spectrum of β-hydroxyethyl peroxy radical (β-HEP) has been recorded in the NIR by cavity ringdown spectroscopy. The precursor, β-hydroxyethyl radical, is generated by photolysis of 2-iodoethanol and by OH-initiated oxidation of ethene, in both cases followed by addition of O 2 to form the peroxy. Although electronic structure calculations predict that 13 conformers of β-HEP exist as minima on the potential energy surface, the experimental spectrum is rationalized in terms of the band origins and vibrational progressions of only the two most stable conformers, G 1 G 2 G 3 and G 1 0 G 2 G 3 .

Spectroscopic studies of the $\tilde{A}$Ö$\tilde{X}$X̃ electronic spectrum of the β-hydroxyethylperoxy radical: Structure and dynamics

“…The peak of the origin band transition of β-HEP has been found to be around 7381 cm −1 in the ambient CRDS experiment 19 with a moderate resolution laser apparatus. Due to the band congestion under room temperature experimental condition, the origin band position was not able to be measured precisely.…”

“…[16][17][18] TheÃ-X origin band of two conformers(G 1 G 2 G 3 and G 1 G 2 G 3 ) of β-HEP have been identified via vibronic analysis of the ambient temperature CRDS spectrum. 19 However, a jet-cooled spectrum is required to confirm the conformational assignment explicitly since the rotational contour in the ambient temperature CRDS cannot be resolved because of congestion.…”

Communication: Theoretical prediction of the structure and spectroscopic properties of the $\tilde{\mathrm{X}}$X̃ and $\tilde{\mathrm{A}}$Ã states of hydroxymethyl peroxy (HOCH2OO) radical

“…The geometry is essentially similar to theX state, except for a significantly elongated O-O bond and a slightly shorter C-O bond, which is very similar to what was found for the HOO radical. [27][28][29] A direct experimental access to the geometry change in theà state of HOCH 2 OO can be found in the rotational constants. The computed rotational constants corresponding to the optimized geometry of theà state are given in Table I.…”

“…The computed rotational constants corresponding to the optimized geometry of theà state are given in Table I. Vertical and adiabaticà −X transition energies for HOCH 2 OO computed at the CASPT2 and RCCSD(T) level of theory are tabulated in Table II 29,30 radical, respectively. This is consistent with the fact that the excitation is very local and hence, the effect of the substituent is limited.…”

Cavity Enhanced Spectroscopy: Applications Theory and Instrumentation

“…Application of CES techniques has provided a means by which absorption crosssections for some radical species can be measured, including nitrate radical, (34) acyl radicals, (35) hydroperoxyl radical, (36) and alkyl peroxy radicals. (37,38) Encyclopedia of Analytical Chemistry, Online …”